Greases thickened with lithium soaps of ethyl hexanoic acid, fatty materials, and esters of 12-hydroxystearic acid



3,053,767 Patented Sept. 11, 1962 oration of Delaware N Drawing. Filed Jan. 26, 1059, Ser. No. 7 88,7 67 13 Claims. (Cl. 25241) This invention relates to new compositions of matter and, in particular, relates to premium grease compositions containing a plurality of thickening components, including a lithium soap of ethyl hexoic acid; and to a method for their preparation. I

A series of commercially available greases containing lithium l2-hydroxy stearate as the thickening component are known in the art as premium greases. These greases are characterized by high dropping point, mechanical stability and other desirable properties and find use in high temperature and other applications characterized by extreme or severe conditions. The cost of the fatty components employed to produce known premium greases is a significant factor, and as greater demands for these greases occur, the problem of cost is aggravated. The present invention, in particular, relates to a new premium grease composition which is characterized by highly desirable properties and is further characterized by employing a lower cost fatty component than heretofore employed for premium lithium greases.

Novel grease compositions have now been discovered which contain as a portion of the thickening component a lithium soap of ethyl hexoic acid. Grease compositions of the present invention thus comprise a mineral based lubricating oil thickened to a grease conslstency with soaps comprising a minor portion of lithium ethyl hexoate and a major portion of other defined lithium soaps. This discovery is surprising when considering that the use of a variety of compounds, for instance, hydroxyacetic acid, azelaic acid, succinic acid, myristic acid, lauric acid, and palmitic acid, were found unsuccessful in this connection.

The essential fatty component of grease compositions of the present invention is ethyl hexoic acid, for example Z-ethyl hexoic acid. This acid normally comprises about 0.1 or 0.25 to 25 or more Weight percent of the total saponifiables employed, for example about 0.5 to percent and preferably about 0.5 to 1 percent. The other saponifiables can include about 15 or 45 to 99.9 percent, preferably about 60 to 79.5 percent, of esters of 12- hydroxy vstearic acid generally containing from about 1 to 5 carbon atoms in the hydrocarbon radical connected to the acyl radical of the ester, e.g. methyl 12-hydroxy stearate, hydrogenated castor oil, etc. The other saponifiables can also include from about 0 to 54.98 or 84.9 percent, and especially about 20 to 35 percent, of other known fatty materials, containing generally from about 12 to 24 carbon atoms per fatty acid radical, employed in grease manufacture such as saturated or unsaturated fats or fatty acids containing from about 12 to 24 carbon atoms per acid radical. All percentages are on the basis of the unsaponified fatty components. Particularly satisfactory conventional fatty materials include, for example, oleic acid, palmitic acid, lauric acid, stearic acid, 12-hydroxy stearic acid and the corresponding glycerides and other ester forms which are saponifiable or whose ester group is replaceable by metal as during neutralization. A fatty component which has been satisfactorily employed in the present invention is Neo Fat 1-54 (also known as Neo Fat 1654), a product of The Armour Company, which is a eutectic composition containing 68 percent palmitic acid, 30 percent stearic acid and 2 percent oleic acid. Another fatty component which yields greases of superior physical characteristics when employed with an ester of 12-hydroxystearic acid and 2- ethyl hexoic acid is Vopcolene 76, a product of Vegetable Oil Products Company, which is a commercial grade 12- hydroxystearic acid. The saponifiables are converted to soap or thickening component by reaction with a suitable lithium containing component, for example, an inorganic compound such as lithium hydroxide and particularly a hydrated lithium hydroxide such as lithium hydroxide monohydrate.

In the preparation of the present grease, the soaps are preperably prepared in situ in the presence of a portion, e.g. at least about 5% of the weight of the finished grease and usually at least an amount equal to one half the weight of the saponifiables, or all of the oil of the final composition. About 10% of starting oil is preferred. Maximum temperatures of about 300 to 425 F. can be used with a maximum processing temperature of about 320 to 350 F. being preferred to form the proper physical characteristics of the soap fibril. Complete saponification usually takes place in about 15 to 20 minutes after maximum temperature is attained. A particularly satisfactory embodiment comprises adding saponifiables and starting oil to a kettle and heating until a substantially complete solution is effected. A hot slurry of lithium hydroxide is then added and the mixture is agitated vigorously while the temperature is raised gradually to evaporate water. During saponification and dehydration, quantities of the oil advantageously are added to limit foaming and maintain the mixture in at least a semi-fluid state. The processing time is generally for a period of time sufficient to eliminate the water in which the lithium hydroxide is dissolved and the water of reaction. After dehydration, it .is advantageous to raise the temperature of the mass to about 300 to 350 F. for periods up to about 1 or 2 hours. At the end of this period, the grease is permitted to cool, or alternatively, further quantities of oil, as necessary or desired, can be added to facilitate cooling. The addition of the usual additives, such as oxidation inhibitors and the like, can then be added and the grease can also be milled in the usual manner, for instance, in a colloid mill with a clearance of about .001 inch. The total amount of soap in the grease is sufficient to provide a product of grease consistency and usually is in the range of about 4 to 20 weight percent of the composition and preferably about 5 to 10%. The oil component employed in the present invention can be any of the mineral lubricating oils employed in the manufacture of premium lithium-containing greases. Thus, the oil can be a mineral lubricating oil obtained from any base crude, as for example, a neutral oil. The oil component can be highly refined if desired or lightly refined as by distillation, solvent extraction, or clay or chemical treatment- Viscosity of the oil component is quite variable and may, for

example, range from about 50 SUS at 100 F. to about 500 SUS at 210 F.; the exact viscosity chosen depends upon the use contemplated. For the majority of applications, a mineral lubricating oil of a viscosity of about 40 to SUS at 210 F. is preferred.

Materials normally incorporated in grease compositions to impart special characteristics can be included in the present compositions. These include, for example,

oxidation inhibitors, corrosion inhibitors, extreme pressure agents, and anti-wear agents. The quantity of additives employed usually ranges from about 0.01 to 10 weight percent and in general, they can be used in any amount desired so long as the grease of the present invention is not deleteriously affected. Normally, additives are incorporated in the grease in conjunction with the finishing oil.

The invention will be described further in conjunction with the following specific example. It should be understood that the invention is not to be limited by the details disclosed in the example. All percentages given in the specification and the example are by weight unless otherwise indicated.

EXAMPLE I About 930 grams of a mineral lubricating oil having a viscosity of about 59 to 61 SUS at 210 F., about 665 grams of hydrogenated castor oil, about 285 grams of Neo Fat l-54, and 50 grams of a Z-ethyl hexoic acid were added to a kettle and heated while agitating the mixture until solution was complete. The temperature was about 200 F. At this point a hot solution of lithium hydroxide monohydrate in water (157 grams of lithium hydroxide in 500 grams of water) was added to the mixture and the temperature gradually raised. As the temperature passed 212 F. evaporation of the water was effected during the time that saponification went to completion. At the end of about 1 hour and 20 minutes the temperature was 338 F. Saponification was complete and the grease mass substantially completely dehydrated. The temperature was maintained at about 340 F. for about 40 minutes. At the end of the cooking period Table II below gives data showing the effects of 2- ethylhexoic acid when used in compounding lithium greases from hydrogenated castor oil mixed with some Neofat l654. Table III presents similar information for lithium greases made from 12-hydroxystearic acid and its methyl ester.

All of these greases were made by esesntially the same method as described above in Example I, in which the fatty materials were first melted and mixed in the compounding kettle with starting oil (mineral oil), usually about of the weight of the finished grease, followed by the addition of hot lithium hydroxide solution to the mixture. After the soap stock ingredients and oil are introduced to the kettle, full steam pressure (135 lbs.) is applied and the temperature is allowed to rise. Saponification and preliminary grease formation were carried out in the kettle with the maximum temperature ranging from 320 F. to 350 F., followed by fairly rapid cooling. Complete saponification usually takes place in 15 to minutes after maximum temperature is attained. The processing time is generally for a period of time SllfilClfiIlt to eliminate the water in which the LiOH-H 0 is dissolved and the water of reaction. The resulting grease was finally processed to its finished form by passing it through a colloid mill with a clearance of .001 inch.

O 2:" the grease was permuted to cool 160 Whereuimn All batches were made in the same equipment from simi- 0.25 percent of Ortholeum 300 (d1phenyl amine oxida- 1 ar quantities of fatty materials, and all portions of each tion inhibitor obtained from duPont) was added and particular type of fatty material were from the same lot. the mass was then colloidally milled in a Charlotte Col- Th e milling conditions for finishing the greases were very loid Mill using a clearance of .003 inch. The resulting case was then anal zed and its r0 erties were deter 3O nearly the same m all cases y P p The mineral oil from which the greases shown in mined; significant data are included in Table I below. For T M I a e were compounded was a blend of solvent refined purposes of comparison data on a second grease compo- C V i ontinent and Western stocks having a viscosity sition according to the present invention and on a known f 60 SUS o 0 at 210 F. and an 88 minimum viscosity index. commercially available premium grease are included. Th

e greases shown in Table II were made from an SAE The commercial grease was prepared according to an in 50 0 rade, naphthenic base (Western), conventionally situ procedure in which the soap was formed from hydrot d a reate oil having a viscosity of about 85 SUS at 210 F. genated castor oil and a lithium-containing compound and aviscosity index of about 18 with final heating at about 400 F.

Table 1 4 Test Grease Second Commet- Table II of exam- Grease ci P18 I of E Grease 1 [Efiects 0f2-ethy1hexoic acid in lithium greases made from hydrogenated csstor oil and neoiat 16-54] Total Soap Content, percent 6. 5 5. 7 6.05 Unworked Penetration at 77 F- sis 337 357 Batch Number 698 659 691 M4 Mechanica 0 ii nwor e 7 5 Penetration at 77 F.Aiter worked: gg gi g gg $652 2? Materials Charge gig 2:2 Hydrogenated Castor Oil 100.0 50.0 00.5 00.5 100 U 5 -"P"; N0o[at1654 (formerly 1-54)- None 500 28.5 28.5 AST DIOPPmg P F 374 366 383 2-Ethylhexoic Acid None Non 5 0 5 0 ASTM Wheel Bearing Test, Gms 1.8 3.2 5. 6 soap Content percent by Weight: Bleedgg d 2211f tmzoF) Lithium 12-Hydroxystearate 8.10 5.73 4.25 3. 74 Aipergengmo S. a n 7 11 4 20 6 gIgoflat 1153-54 soa p- None 0.00 1.91 1.07 MR 2 2 2 r 4 10.0 55 isntii $t;2ti0li1i?i::: it 5352 it 2%? Pressure VISCOSIW Penetration at 77 F,, Worked 100,000

F 222 222 222 222 522 222 I a 1 2 v SSU at 00 F 50 000 507 000 5 000 ASTM pp Pomt, o F 383 380 574 366 2t 2 222 2 222 22 SSU M130 i 1 l Attempts to make a grease with mineral lubrlcating oil usiu onl SSU at F 3'25O 11180 lithium 2-cthy1hexoate in amounts of 5, 10, 15 and 25%, resp i iv ly were unsuccessful because the oil (lid not thicken suilicicntly.

1 Fatty component entirely hydrogenated eastor oil.

Table III [Efiects of 2ethylhexoie acid in lithium 12-hydroxystearate greases made from the fatty acid and the methyl ester] Batch Number 482 964 905 906 907 908 009 070 071 Composition of Fatty Materials Charge, percent by Weight:

IQ-Hydroxystearic Acid 95.0 None None None None None None None Methyl IZ-Hydroxystearate None 95.0 99.0 99.5 99.5 99.9 99.98 100.00 2-Ethylhcxoic Acid 5.0 5.0 1.0 0. 5 0.5 0.1 0.02 None Soap Content, percent by Weight:

Lithium 12-Hydroxystearate... 7.58 7. 57 7.90 0. 97 5. 07 8.00 8.00 8.00 Lithium Z-Ethylhexoate..- 0.41 0. 43 0.09 0. 04 0. 03 0.01 0. 0010 None ASTM Penetration 372 L0. 237 273 291 317 305 312 317 ASTM Dropping Point, F.. 373 384 388 383 377 388 382 352 LO. Light cone penetration.

The above data in Table I demonstrate that the greases of the present invention are especially desirable premium greases and show at least comparable properties as regards yield and pressure viscosity temperature relations when compared with the known premium grease. The other characteristics of the present grease are also shown to be highly desirable when compared to those of the commercial lithium grease. For example, the improved stability of greases of the invention is clearly evident in the bleed test wherein significant resistance to separation is shown.

It may be seen from Tables 11 and III that the inclusion of a small amount of 2-ethylhexoic acid in the fatty materials greatly improves the thickening capacity of soap formed from hydrogenated castor oil and methyl 12- hydroxy stearate, but has little or no beneficial effect on soap formed from 12-hydroxystearic acid alone, that is without the methyl ester. In greases made from the glycen'de and methyl ester, the use of Z-ethyl-hexoic acid substantially reduces the amount of soap needed to give a certain consistency, and also permits the use of large amounts of less expensive fatty materials, such as Neofat 1654, for soap formation while still retaining very good yields and other desirable properties. This will permit substantial savings in the cost of materials for a grease. By comparing batch 968 with batch 971 it is seen that the use of 0.5 percent of Z-ethylhexoic acid in the fatty materials charge brought about a 25 percent reduction in soap content (from 8 percent to 6 percent) for the same worked penetration. It is noteworthy that the use of 2-ethylhexoic acid with the methyl ester also greatly increased the early SZbPOIllfiCaJfiOIl rate and that the use of lithium 2-ethyl hexoate alone was unsatisfactory as a thickening component.

This application is a continuation-in-part of application Serial No. 524,588, filed July 26, 1955, now abandoned.

It is claimed:

'1. A grease composition consisting essentially of a mineral base lubricating oil thickened to grease consistency with lithium soaps of sapon-ifi-ables consisting essentially of about 0.1 to 25 percent of ethyl hexoic acid, about to 84.9 percent of fatty materials containing from about 12 to 24 carbon atoms per acid radical, and about 15 to 99.9 percent of an ester of 12-hydroxy stearic acid.

2. The grease composition of claim 1 wherein the ethylhexoic acid is Z-ethylhexoic acid.

3. The grease composition of claim 2 wherein the ester of 12-hydroxy stearic acid contains from about 1 to 5 carbon atoms in the hydrocarbon radical connected to the acyl radical of the ester.

4. The grease composition of claim 2 wherein the ester of lZ-hydroxy stearic acid is hydrogenated castor oil.

5. A grease composition consisting essentially of a.

mineral base lubricating oil thickened to grease consistency with lithium soaps of saponifiables consisting essen tially of about 0.5 to 5 weight percent of 2-ethy1 hexoic acid, about to 79.5 weight percent of the ester of 112- hydroxy stearic acid and about 2-0 to 35 weight percent of fatty materials of about 12 to 24 carbon atoms per acid radical.

6. The grease composition of claim 5 in which the fatty materials of about 12 to 24 carbon atoms per acid radical is a mixture of fatty acids consisting essentially of 68 percent palmitic, 30 percent stearic acid and 2 percent :oleic acid.

7. A grease composition consisting essentially of a mineral base lubricating oil thickened to grease consistency with lithium soaps of saponifiables consisting essentially of about 0.1 to 25 percent of Z-ethyl hexoic acid and about 15 to 99.9 percent of an ester of 12-hydroxy stearic acid.

8. A method for the preparation of a grease composition which consists essentially of a mineral base lubricating oil thickened to grease consistency with lithium soaps of saponifiables consisting essentially of about 0.1 to 25% ethylhexoic acid, 0 to 84.9 of fatty acids containing from about 12 to 24 carbon atoms per acid radical and about 15 to 99.9 percent of an ester of 12-hydroxy stearic acid; the steps comprising forming a mixture of saponifiables comprising ethyl hexoic acid, fatty materials containing from about 12 to 24 carbon atoms per acid radical, and an ester of 12-hydroxy stearic acid, with a mineral base lubricating oil; heating the mixture to effect a substantially complete solution; adding a lithium containing component to the solution to convert the saponifiables to soaps; and heating the solution to effect substantially complete saponifioation and dehydration to form the grease.

9. The method of claim 8 wherein the ethyl hexoic acid is 2-ethyl hexoic acid.

10. The method of claim 9 wherein the ester of 12- hydroxy stearic acid contains from about 1 to 5 carbon atoms in the hydrocarbon radical connected to the acyl radical of the ester.

11. The method of claim 9 wherein the ester is hydrogenated castor oil.

12. The method of claim 9 wherein the amount of mineral base lubricating oil present during soap formation is about 10% based on the finished grease.

13. The method of claim 12 in which the dehydrated grease is milled in a colloid mill at about 0.001 inch clearance.

References Cited in the file of this patent UNITED STATES PATENTS 2,274,676 Earle Mar. 3, 1942 2,606,153 Holdstock Aug. 5, 1952 2,628,195 Allison et a1. Feb. 10, 1953 2,628,202 Allison et al. Feb. 10, 1953 2,651,616 Mathews et a1. Sept. 8, 1953 2,883,341 Allison Apr. 21, 1959 

1. A GREASE COMPOSITION CONSISTING ESSENTIALLY OF A MINERAL BASE LUBRICATING OIL THICKENED TO GREASE CONSISTENCY WITH LITHIUM SOAPS OF SAPONIFIABLES CONSISTING ESSENTIALLY OF ABOUT 0.1 TO 25 PERCENT OF EHTYL HEXOIC ACID, ABOUT 0 TO 84.9 PERCENT OF FATTY MATERIALS CONTAINING FROM ABOUT 12 TO 24 CARBON ATOMS PER ACID RADICAL, AND ABOUT 15 TO 99.9 PERCENT OF AN ESTER OF 12-HYDROXY STEARIC ACID. 